1. Technical Field
The present invention relates to an electric motor control apparatus which detects magnetic pole positions of a rotor by means of a plurality of position sensors, and controls an electric motor based on a plurality of position sensor signals (detected magnetic pole positions).
2. Description of the Related Art
In general, in an electric motor control apparatus which detects a magnetic pole position of a rotor by the use of a position sensor thereby to control an electric motor, in cases where the position sensor fails, there will be a problem that it becomes impossible to control the electric motor in a normal or ordinary manner.
Accordingly, there has been proposed a technique in which a magnetic pole position estimation means for estimating a magnetic pole position of a rotor is separately provided other than a position sensor, and a determination as to the presence or absence of failure of the position sensor is performed by making a comparison between a signal output from the position sensor (a detected value of the magnetic pole position) and an estimated value of the magnetic pole position (for example, see a first patent document).
In the first patent document, a means for detecting the phase of an induction voltage generated in a stator (armature) during the rotation of an electric motor is used as the magnetic pole position estimation means.